Gas-pressured medication delivery service

ABSTRACT

The present invention relates to medical devices and particularly to a medication delivery device for self-injection of a medication, or for healthcare professionals to administer a medication. In one embodiment, a medication delivery device utilizes a source of gas pressure to deploy a needle, deliver a desired amount of medication through the needle, and retract the needle for disposal. Fluid flow paths from the source of gas pressure communicate the gas pressure to the needle and to the medication in order to accomplish these steps. In one embodiment, a valve is positioned to open and close the flow of the pressurized gas to the needle and the flow of the medication to the needle, so that the valve can be operated to deploy the needle and deliver the medication through the needle when the user is ready for the injection. The valve can also be operated to retract the needle when the dose is complete.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 61/315,893, filed on Mar. 19, 2010, the entire contentof which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to medical devices and particularly to amedication delivery device for self-injection of a medication.

BACKGROUND

In various situations, it is desirable or even medically necessary forpatients to self-administer medication away from a doctor's office orprofessional medical setting. Such medication may take the form of aliquid or reconstitutable liquid drug administered by sub-cutaneous orintramuscular needle injection. Various medical devices have beendeveloped to enable patients to perform these self-injections withoutthe assistance of a medical professional.

An example of an injection device is shown in U.S. Pat. No. 5,616,132.This patent discloses a portable medicant injection device with a needlethat moves when pressurized gas is released into a housing. The userpresses downwardly on the device to release the gas, which forces adiaphragm downwardly, carrying the needle with it. The gas pressure alsomoves a plunger downwardly to force the medication through the needle.After the gas escapes, the diaphragm returns to its normal position,withdrawing the needle.

Many drug delivery devices utilize stored energy to insert the needleinto the patient and deliver the medication. This energy can be storedin the form of material resiliency, compressed springs, magnets,batteries, pressurized gas, or chemical reaction. A combination of thesecomponents may be utilized, along with other mechanical components suchas ratchets, levers, and hinges. These various moving parts and energysources can be complicated for the patient to use. Accordingly, there isstill a need for a medication delivery device that is simple to use andenables the patient to safely inject a needle, deliver a desired dose ofmedication, and dispose of the used needle without professional medicalassistance.

SUMMARY OF THE INVENTION

The present invention relates to medical devices and particularly to amedication delivery device for self-injection of a medication, or forhealthcare professionals to administer a medication. In one embodiment,a medication delivery device utilizes a source of gas pressure to deploya needle, deliver a desired amount of medication through the needle, andretract the needle for disposal. Fluid flow paths from the source of gaspressure communicate the gas pressure to the needle and to themedication in order to accomplish these steps. In another embodiment, avalve is positioned to open and close the flow of the pressurized gas tothe needle and the flow of the medication to the needle, so that thevalve can be operated to deploy the needle and deliver the medicationthrough the needle when the user is ready for the injection. The valvecan also be operated to retract the needle when the dose is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of a medication delivery deviceaccording to an embodiment of the invention.

FIG. 2 is a front perspective view of the device of FIG. 1, with thecover removed.

FIG. 3 is a rear perspective view of the device of FIG. 1, taken alongthe cross-section 3-3 in FIG. 2.

FIG. 4A is an exploded perspective view of a piston and needle assemblyaccording to an embodiment of the invention.

FIG. 4B is a cross-sectional view of the piston and needle assembly ofFIG. 4A in a retracted position.

FIG. 4C is a cross-sectional view of the piston and needle assembly ofFIG. 4A in a deployed position.

FIG. 5 is an exploded view of a valve according to an embodiment of theinvention.

FIG. 6 is a top view of a medication delivery device according to anembodiment of the invention, with the cover removed and the valve shownin cross-section, for clarity, in a retracted position.

FIG. 7 is a top view of a medication delivery device of FIG. 6 in adeployed position.

FIG. 8 is a perspective view of a medication delivery device accordingto another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to medical devices and particularly to amedication delivery device for self-injection of a medication, or forhealthcare professionals to administer a medication. In one embodiment,a medication delivery device utilizes a source of gas pressure to deploya needle, deliver a desired amount of medication through the needle, andretract the needle for disposal. Fluid flow paths from the source of gaspressure communicate the gas pressure to the needle and to themedication in order to accomplish these steps. In one embodiment, avalve is positioned to open and close the flow of the pressurized gas tothe needle and the flow of the medication to the needle, so that thevalve can be operated to deploy the needle and deliver the medicationthrough the needle when the user is ready for the injection. The valvecan also be operated to retract the needle when the dose is complete.

An embodiment of a medication delivery device 10 is shown in FIG. 1. Thedevice includes a cover 12 that slidably fits over a base 14. Thevarious active components of the device are mounted to the base andenclosed under the cover. In the embodiment shown, the cover 12 includesthree openings 16 a, 16 b, 16 c. The first two openings 16 a, 16 b areaccess windows for operating the valve 18, which will be described infurther detail below. The third opening 16 c allows an activation button20 to pass through the cover 12 and extend upwardly for the patient'suse.

The device 10 with the cover 12 removed is shown in FIG. 2. Mounted tothe base 14 are the main components of the drug delivery device,including the valve 18, a medication reservoir 24, a piston assembly 26,and a power cell such as a pressure housing 28. The medication reservoir24 includes a liquid medication, such as a liquid drug or a solution orsuspension of a solid drug. The piston assembly 26 includes a piston 30that slides up and down over a piston housing 32. The piston 30 isconnected to a needle 34 (shown in FIG. 3). The piston 30 moves up anddown to deploy and retract the needle. The pressure housing 28 includesa source of gas pressure (described in further detail below) which isrouted through the device 10 to deploy the needle and deliver themedication. The valve 18 controls the flow of gas pressure andmedication to the piston assembly 26.

The device 10 has several flow paths for fluid flow within the device,including flow of gas pressure and medication. These flow paths areintroduced here and described in detail below. A first pressure flowpath 40 extends from the pressure housing 28 to the medication reservoir24, to apply pressure to the liquid medication to cause it to flow tothe needle. A medication flow path 44 extends from the medicationreservoir 24, through the valve 18 and to the needle 34, so thatmedication flows through the needle into the user's skin. A secondpressure flow path 150 (see FIG. 6) extends from the pressure housing 28to a downwardly-facing surface of the piston 30. Gas pressure from thispath raises the piston 30 into the retracted position, retracting theneedle inside the device 10. A third pressure flow path 152 (see FIG. 7)extends from the pressure housing 28 to an upwardly-facing surface ofthe piston 30. Gas pressure from this path pushes the piston down intothe deployed position, with the needle extending from the device 10 tobe inserted into the user's skin. The valve 18 is moved to alternatebetween opening the second flow path and closing the third flow path (toraise the piston) and opening the third flow path and closing the secondflow path (to lower the piston). When either the second or third flowpath is closed, a corresponding vent path is opened to vent the oppositeside of the piston. This allows the piston to be moved up and down bythe gas pressure when the user operates the valve.

With this introduction, the specific components of the device 10 willnow be described. As shown in FIG. 2, the pressure housing includes anoutlet 38, through which the gas pressure from the pressure housingflows to the various components in the device. The medication reservoir24 includes an inlet 36 for receiving this gas pressure. The firstpressure flow path 40 connects the outlet 38 of the pressure housing 28to the inlet 36 of the medication reservoir 24. The flow path 40fluidically couples the pressure housing 28 to the medication reservoir24, meaning that a path for fluid communication exists between thepressure housing 28 and the medication reservoir 24. In the embodimentshown, the first pressure flow path 40 includes a tube or conduit 42that is connected at one end to the outlet 38 of the pressure housing 28and at the opposite end to the inlet 36 of the medication reservoir 24.When the user presses the activation button 20 and builds gas pressurein the pressure housing 24 (as described in further detail below), thegas pressure flows through the tube 42 along the first pressure flowpath 40 through the inlet 36 and into the medication reservoir 24, wherethe gas exerts pressure on the liquid medication to cause it to flow tothe needle 34.

The gas pressure in the first pressure flow path 40 pushes themedication in the medication reservoir 24 and causes it to flow from themedication reservoir 24 through an outlet 46 and through the medicationflow path 44 to the needle 34 (see FIG. 3). The medication flow path 44fluidically couples the medication reservoir 24 to the needle 34,through the valve 18. The medication flow path 44 passes into an inlet48 a on a first side of the valve 18 and out of an outlet 48 b on theopposite side of the valve 18. The valve itself is moved to allow orblock flow of the medication through the valve, between this inlet 48 aand outlet 48 b. The flow path 44 includes a tube or conduit, which isdivided into a first tube portion 50 a extending from the medicationoutlet 46 to the valve inlet 48 a, and a second tube portion 50 bextending from the valve outlet 48 b to the needle 34.

Referring now to FIG. 3, the medication reservoir 24 includes a lid 52attached to the base 14 by fasteners such as screws 54. The lid 52 andthe base 14 each include a matching depression 56 a, 56 b, respectively,that face each other when the lid 52 is attached. The depressions form acavity 58 where the liquid medication is stored. The medication may bestored directly within the cavity 58, or it may be included in a sealedbag within the cavity 58. In either case, the medication reservoir 24may include a flexible membrane 60 arched across the cavity 58 andmatching the shape of the depression 56 a. When the gas pressure fromthe pressure housing 28 flows through the first pressure flow path 40 tothe medication reservoir 24, the gas pressure pushes on this membrane60, which flexes downwardly and pushes on the medication in the cavity58. The membrane 60 continues to flex downwardly as the medication flowsfrom the cavity 58, until the membrane 60 reaches its mirror-image shapeon the bottom of the cavity 58, along depression 56 b, as shown indotted lines in FIG. 3. In this position the membrane 60 matches thedepression 56 b so that no medication (or only a small trace amount)remains in the reservoir 24. The membrane 60 may be made of a flexiblemultilayer polymeric film.

When the medication flows from the cavity 58, it flows through an exitflow path 62 to the outlet 46. The exit flow path 62 is formed as achannel in a raised portion of the base 14, connecting the depression 56b to the outlet 46. From there the medication flows along the medicationflow path 44 (shown in FIG. 2)—through the tube portion 50 a, throughthe valve 18, and through the tube portion 50 b to the needle 34, asdescribed before.

Still referring to FIG. 3, the medication reservoir 24 also includes afill port or septum 64 through which liquid medication can be insertedby needle injection into the cavity 58. The cavity 58 can be pre-filledwith medication, or the medication can be inserted into the cavitythrough the fill port 64. The fill port 64 can also be used to inject adiluent into the cavity 58 to create a solution or suspension with asolid drug stored in the cavity 58. The fill port 64 is formed in araised portion of the base 14 and is fluidically coupled to thedepression 56 b and into the cavity 58.

Turning now to the pressure housing 28, as shown in FIG. 3 the pressurehousing 28 includes a reaction chamber 64 enclosed by a lid 66. Theactivation button 20 extends upwardly from the lid 66. The reactionchamber 64 includes a source of gas pressure 68. In the embodimentshown, the source of gas pressure 68 includes two chemical components70, 72 that generate gas as a byproduct when the two components react.In one embodiment, the first component 70 is calcium carbonate and thesecond component 72 is citric acid. When these two components contacteach other, they undergo a chemical reaction that generates carbondioxide. This generation of carbon dioxide builds gas pressure withinthe reaction chamber 64.

The two reactants 70, 72 are stored separately from each other insidethe reactant chamber 64, beneath the lid 66 and the activation button20. Before the user is ready to operate the device, the reactants remainseparated and no gas pressure is generated. The first pressure flow path40 (see FIG. 2) from the pressure housing 28 to the medication reservoir24 and the second and third pressure flow paths 150, 152 (see FIGS. 6-7)from the pressure housing 28 to the piston assembly 26 are notpressurized, as no gas pressure has been generated or released.

In order to operate the device and release the gas pressure, the userpresses the activation button 20. The activation button 20 is connectedto the lid 66 via a frangible connection 74. When the activation button20 is pressed, the connection 74 is broken and the button 20 movesdownwardly into the reactant chamber 64. A lower end 20 a of the button20 contacts the first reactant 70 and breaks a seal or otherwise movesthe first reactant 70 into contact with the second reactant 72,initiating the chemical reaction and the generation of gas pressure.When the reactants are calcium carbonate and citric acid, the calciumcarbonate may be stored as the first reactant 70 above the citric acid72, so that the activation button 20 pushes the calcium carbonate 70down into the liquid reservoir of citric acid 72. The calcium carbonate70 can be provided in the form of a solid tablet, a powder, or acombination of a solid tablet and powder. These reactants can bepackaged and stored within the pressure housing 28 in other ways aswell. For example, the citric acid may be stored above the calciumcarbonate, and the button 20 may rupture a seal to allow the citric acidto flow down over the calcium carbonate.

In one embodiment, the gas pressure generated by the reactants 70, 72 issufficient to drive flow of the medication for a prolonged duration, todeliver a large volume sub-cutaneous injection. The volume of medicationdelivered by the device into the user's skin can vary from 1 mL to 300mL depending on the situation. In one embodiment the volume ofmedication is approximately 10 mL. The source of gas pressure delivers arapid burst of pressure, to inject the needle and cause the medicationto flow through the needle for the duration of the injection until thedose is complete. In one embodiment, the pressure delivered by thesource of gas pressure is approximately 20 psi at the time ofactivation, and falls to about 12 psi at the time of completion of thedose. The delivery time can vary from a few seconds to 10 minutes. Inone embodiment, approximately 24 psi of pressure is generated within 5seconds of activation of the pressure source, and the resultingmedication flow rate is approximately 0.5 mL per second through a 27gauge needle that is ½ inches in length. The device can be designed todeliver medication at flow rates ranging from 0.5 mL/second to 0.5mL/minute.

The gas pressure builds inside the reactant chamber 64 and flows throughan outlet path 76 which fluidically couples the reactant chamber 64 tothe pressure outlet 38. From there, the gas flows through the firstpressure flow path 40 (see FIG. 2) and through either the second orthird pressure flow paths 150, 152 (see FIGS. 6-7) to deploy or raisethe piston and to cause the liquid medication to flow to the needle (asdescribed in further detail below). The path 76 also fluidically couplesthe reactant chamber 64 to a pressure relief valve 78. This pressurerelief valve 78 is a safety feature that vents the gas within thechamber 64 in the case of over-pressurization.

As just described, the pressure housing 28 includes a source 68 of gaspressure that is activated by the user to cause gas to flow through thefirst pressure flow path 40 to the medication reservoir and through thesecond or third flow paths 150, 152 to the piston assembly 26. Thepiston assembly 26 is now described in reference to FIGS. 4A-4C. Thepiston assembly 26 includes the piston 30 that is movable over thepiston housing 32. The piston 30 includes a hub 80 that is attached tothe needle 34. The hub 80 is rigidly attached to the piston 30 so thatthe needle 34 moves with the piston 30. The hub 80 also includes a fluidinlet 82 that is connected to the medication flow path 44 (shown in FIG.2), allowing medication to flow from the medication flow path 44 throughthe inlet 82 to the needle 34. The needle 34 itself is a hollow needlewith a pointed distal end and a lumen through the needle for the flow ofmedication to the user. The distal end of the needle may be beveled.

The piston housing 32 is cylindrical in shape and includes a hollowinterior chamber 84 with an inside surface 32 a. The chamber 84 isclosed on the lower end by the base 14 of the device 10, and on theupper end by a lid 86 (see FIGS. 4B-4C). The lid 86 and the pistonhousing 32 include matching wings or extensions 88 a, 88 b(respectively) that align when the lid 86 is placed onto the pistonhousing 32. Screws or other fasteners pass through the wings 88 a intothe wings 88 b to attach the lid 86 to the piston housing 32. The lid 86includes a central opening 90 for passage of the piston 30, to allow thepiston 30 to move up and down. Lastly, the lid 86 includes an o-ring orother seal 94 that contacts the inside surface 32 a of the pistonhousing 32 when the lid is attached to the housing, as shown in FIGS.4B-4C. When the lid 86 is attached to the piston housing 32 via thewings 88 a, 88 b, the o-ring 94 creates an airtight seal at the top ofthe interior chamber 84. This seal contains the gas pressure that isrouted to this interior chamber 84 to move the piston 30 up and down, asdescribed in further detail below.

The piston 30 includes an outer shell 96, a post 102, and a plate 104.The plate 104 has a top, upwardly facing surface 105 and a bottom,downwardly facing surface 107. The shell 96 is cylindrical and is shapedand sized to pass over the piston housing 32. The shell 96 includescutouts 98 that align with and engage the wings 88 a, 88 b. Theengagement of the wings 88 a, 88 b in the cutouts 98 allows the shell 96to move vertically along the piston housing and prevents the shell 96from rotating around the piston housing 32. The shell 96 also includes aseparate cutout 100 which aligns with an inlet 91 at the base of thehousing 32 (described below) and aligns with an inlet 92 on the lid 86,so that the shell 96 can move downwardly over these inlets (see forexample FIG. 2).

The post 102 connects the shell 96 to the plate 104. The post 102extends from the plate 104 through the opening 90 in the lid 86 and isfirmly mounted to the shell 96, such as by adhering the post 102 to anunderside of the shell 96 or securing the post 102 to the shell 96 byfasteners such as screws. The shell 96, post 102, and plate 104 movetogether, sliding up and down over the piston housing 32 with the post102 sliding through the opening 90 in the lid 86. The plate 104 includesan o-ring or other seal 108 that seals against the inside surface 32 aof the base 32, inside the chamber 84. This o-ring 108 creates anairtight seal inside the housing 32 to contain gas pressure from thepressure housing, as described further below.

The piston 30 moves between two positions, as shown in FIGS. 4B and 4C.The movement of the piston 30 is caused by air flow through two separateinlets into the chamber 84. A first inlet 91 is located at the bottom ofthe housing 32, below the lid 86 and below the plate 104. A second inletis located at the top of the lid 86 and connects to a passage 92 athrough the lid 86 into the chamber 84 above the top surface 105 of theplate 104. Thus, the lower inlet 91 leads to the chamber 84 below thebottom surface 107 of plate 104, and the upper inlet 92 leads to thechamber 84 above the top surface 105 of the plate 104.

The lower inlet 91 fluidically couples the second pressure flow path 150to the chamber 84 below the plate 104, so that gas pressure flowingthrough this path enters the chamber 84 and pushes on the bottom,downwardly facing surface 107 of the plate 104 to raise the piston 30into the retracted position, as shown in FIG. 4B. The upper inlet 92fluidically couples the third pressure flow path 152 to the chamber 84above the plate 104, so that gas pressure flowing through this pathenters the chamber 84 and pushes on the top, upwardly facing surface 105of the plate 104 to push the piston down into the deployed position, asshown in FIG. 4C.

In the retracted position of FIG. 4B, the needle 34 is contained withinthe device 10, above the base 14 and inside the cover 12. The plate 104is raised to the lid 86. Air pressure in the chamber 84 below the plate104 retains the piston 30 in this retracted position. This air pressureis sealed by the o-ring 108 on the plate 104.

In the deployed position of FIG. 4C, the needle 34 extends through anopening 110 in the base 14, extending out of the device 10 and into theuser's skin. Air pressure in the chamber 84 above the plate 104 retainsthe piston 30 in this deployed position. This air pressure is sealedbetween the o-rings 94 and 108 on the lid 86 and plate 104,respectively. The piston plate 104 is near the bottom of the housing 32,but above the lower inlet 91, so that the o-ring seal 108 remains abovethe inlet 91 and prevents any gas leakage through the inlet 91. Theshell 96 rests on the lid 86, preventing any further downward travel ofthe piston 30. The height of the shell 96 determines the stroke oftravel of the needle 34, and thus determine the depth of penetration ofthe needle into the user's skin. In one embodiment, the depth ofinjection is 6-9 mm, and the height of the piston is slightly largerthan that depth in order to move the needle from its retracted positionabove the base 14 through the base 14 and to the desired depth ofinjection. Additional information regarding the appropriate depths forsubcutaneous needle injection can be found in the figures anddescription of U.S. Pat. No. 6,544,238.

As indicated by FIGS. 4B and 4C, alternating air pressure between thelower inlet 91 and the upper inlet 92 causes the piston 30 to move upand down. When one inlet is pressurized, the other inlet is vented, sothat the piston 30 can travel through the chamber 84. The gas pressurepaths 150, 152 and vent paths 154, 156 are described in further detailbelow in connection with FIGS. 6-7.

The flow of gas pressure to the piston assembly 26 to raise and lowerthe piston 30 is controlled by the valve 18, which is shown in FIG. 5.The valve 18 interrupts the medication flow path from the medicationreservoir to the needle and interrupts the second and third pressureflow paths from the pressure housing 28 to the piston assembly 26, inorder to control the insertion of the needle and the delivery ofmedication through the needle. In the embodiment shown, the valve 18 isa spool-type valve with a spool 112 that reciprocates within a valvehousing 114. The valve housing 114 includes a central channel 116through which the spool 112 extends.

The spool 112 and housing 114 include openings, seals, and grooves thatare positioned to allow or block gas pressure and medication to thepiston assembly 26. The spool 112 is moved back and forth within thehousing 114 between two different positions (a start position and a stopposition) in order to open and close various flow paths through thevalve. By sliding the spool in one direction or the other within thechannel 116, the grooves and seals on the spool 112 align with openingsin the housing 114 to open and close the flow paths to the pistonassembly 26.

In the embodiment of FIG. 5, the openings on the housing 114 include twoopenings for the flow of medication and three openings and two vents forthe flow of gas pressure. The two openings for the medication flow arethe inlet 48 a and outlet 48 b described above in reference to FIG. 2.The inlet and outlet 48 a, 48 b pass through the valve housing 114 tothe channel 116. The medication flows from the medication reservoir 24through the tube 50 a into the inlet 48 a on the valve housing. Thespool 112 then either allows or blocks further flow of the medication.The medication flow path 44 continues through the outlet 48 b on theopposite side of the housing 114 and through the tube 50 b to the needle34.

The valve housing 114 also includes three openings 120, 122, and 124 forrouting the flow of gas pressure from the pressure housing 28. Theseopenings pass through the housing 114 to the channel 116. The openingsare fluidically coupled to the first and second pressure flow paths 150,152. On the opposite side of the housing 114 from these openings120-124, two vent ports 126, 128 are provided (see FIG. 2) which passthrough the housing 114 to the channel 116. These openings 120, 122, 124and vent ports 126, 126 are alternatively opened or closed to each otherby movement of the spool 112.

The spool 112 includes two opposite ends, the first end forming a startbutton 130 and the second opposite end forming a stop button 132. Theuser pushes on these opposite ends of the spool to operate the valve 18.Along the length of the spool are four spaced-apart o-rings 134 a, 134b, 134 c, 134 d. Between the o-ring 134 d and the stop button 132 is awider liquid seal 140. Between the o-rings 134 a and 134 b and betweenthe o-rings 134 b and 134 c are indentations 136, 138 (respectively)which form flow paths for the gas pressure. A groove 142 is includedbetween the liquid seal 140 and the o-ring 134 d.

These features on the spool 112 and housing 114 are shown incross-section in FIGS. 6-7 to show operation of the valve 18 and theflow of liquid and gas through the valve in its start and stoppositions. FIG. 6 shows the valve 18 in the stop position, with the stopbutton 132 on the spool 112 contacting the housing 114, and the startbutton 130 extending out of the housing and ready to be pressed. In thisstopped position, the valve 18 prevents fluid flow through themedication flow path 44 to the needle. The valve 18 also opens thesecond pressure flow path 150 to the bottom of the piston 30 and closesthe third pressure flow path 152 to the top of the piston 30.Additionally, the valve 18 opens the upper vent path 154 from the top ofthe piston to the vent port 126, and closes the lower vent path 156 fromthe bottom of the piston to the vent port 128. Each of these flow pathsare described in detail below. In FIGS. 6 and 7, the first pressure flowpath 40 (from the pressure housing 28 through tube 42 to the medicationreservoir 24) is omitted for clarity (shown in FIG. 2).

Referring to FIG. 6, with the valve 18 in the stopped position, theliquid seal 140 blocks the medication flow path 44 between the inlet 48a and the outlet 48 b on the valve housing 114. In this embodiment, themedication flow path 44 is larger in cross-sectional area than thevarious gas pressure flow paths, to overcome friction along the tubesand allow smooth flow of the liquid medication to the needle. As aresult, the liquid seal 140 is wider than the a-rings 134 a-d in orderto fully seal the medication flow path 44. With the valve 18 in thestopped position, prior to use of the device by the user, the liquidmedication may flow from the medication reservoir through tube 50 a tothe inlet 48 a. However, with the valve in the stopped position asshown, the liquid seal 140 prevents any further flow of medication. Themedication does not pass around this seal 140 and does not reach thetube 50 b leading to the needle 34. The valve 18 thus prevents anypremature delivery of medication to the needle.

Still referring to FIG. 6, in the stopped position, the valve 18 opensthe second pressure flow path 150. This flow path 150 fluidicallycouples the pressure housing 28 to the piston assembly 26. Specifically,the flow path 150 connects at one end to the outlet 38 of the pressurehousing and at the opposite end to the lower inlet 91 of the housing 32.Gas flow through this lower inlet 91 enters the chamber 84 below theplate 104 and presses on the downwardly facing surface 105 of the plate104, thereby raising the plate and the piston into the retractedposition. The flow path 150 includes a first tube 144 from the outlet 38of the pressure housing 28 to the opening 122 in the valve housing 114,and a second tube 146 from the opening 120 in the valve housing 114 tothe inlet 91. The flow path 150 passes through the first tube 144,through the opening 122 in the housing 114, through the indentation 138in the spool 112, through the opening 120 in the housing 114, andthrough the second tube 146 into the inlet 91.

In the stopped position, the indentation 138 in the spool 112 alignswith the two openings 120, 122 in the housing 114 in order to open thesecond pressure flow path 150. The two tubes 144 and 146 are connectedby this indentation 138 in the spool 112. The o-rings 134 b and 134 c oneither side of the indentation 138 constrain the gas to flow from thefirst tube 144 into the second tube 146. The o-rings 134 b and 134 cprevent the gas from leaking through the valve 18 and escaping throughany other path. Thus in this position, pressure is routed from thepressure housing 28 to the inlet 91 below the plate 104, to lift thepiston 30. Flow through this pressure flow path 150 is indicated bydotted arrows in FIG. 6.

Still referring to FIG. 6, in the stopped position, the valve 18 alsoopens the upper vent path 154. This path 154 fluidically couples theupper inlet 92 (above the plate 104) to the vent port 126. This path 154allows air above the plate 104 to be vented as the plate 104 movesupward due to the pressure below the plate 104 from the second pressureflow path 150. The upper vent path 154 includes a third tube 148 thatconnects the upper inlet 92 to the opening 124 in the valve housing 114.From there the vent path 154 passes through indentation 136 to the ventport 126. The vent port 126 opens to the surrounding air, below thecover 12 (see FIG. 1).

In the stopped position of the valve, the indentation 136 aligns withthe opening 124 and the vent port 126 to open the upper vent path 154.The opening 124 and the vent port 126 are connected by this indentation136 on the spool 112. The o-rings 134 a, 134 b on either side of theindentation 136 constrain the air in this path to flow from the tube 148into the vent port 126. These o-rings prevent the air from leakingthrough the valve 18 and escaping through another path. Thus in thisposition, the air in the chamber 84 above the plate 104 passes throughthe upper vent path 154 and out the vent port 126. This path is shown bythe solid arrows in FIG. 6.

Thus, the valve 18 in the stopped position of FIG. 6 closes themedication flow path 44 (via seal 140), opens the second pressure flowpath 150 (via indentation 138), and opens the upper vent path 154 (viaindentation 136). As a result, medication is prevented from flowing tothe needle, and the piston 30 is raised into the retracted position.

FIG. 7 shows the valve 18 in the start position. The spool 112 has beenmoved in the direction from the start button 130 toward the stop button132 (downwardly in the orientation of FIG. 7) until the start button 130contacts the housing 114. The stop button 132 extends from the oppositeend of the housing 114, ready to be pressed to stop the operation of thedevice. In this position, the spool 112 opens the medication flow path44, closes the second pressure flow path 150, closes the upper vent path154, opens the third pressure flow path 152, and opens the lower ventpath 156. These flow paths are each described in detail below.

As shown in FIG. 7, in the start position, the groove 142 on the spool112 between the liquid seal 140 and the o-ring 134 d is aligned with themedication flow path 44, between the inlet 48 a and outlet 48 b on thevalve housing 114. This alignment opens the medication flow path 44, asthe liquid seal 140 no longer blocks flow between the inlet 48 a andoutlet 48 b. When the pressure from the pressure housing 28 isgenerated, it flows through the first pressure flow path 40 (see FIG. 2)into the medication reservoir 24 and pushes on the flexible membrane 60to push the liquid medication through the outlet 46 into the tube 50 a.With the valve 18 in the start position, the liquid medication flowsfrom the tube 50 a through the inlet 48 a, through the groove 142,through the outlet 48 b, and through the tube 50 b to the needle 34.

Additionally, when the valve 18 is moved to the start position, thesecond pressure flow path 150 (shown in FIG. 6) is closed. The o-ring134 b is positioned between the opening 122 and the opening 120 in thevalve housing 114, thereby blocking air flow from the tube 144 to thetube 146. This o-ring 134 b interrupts the flow path 150 by preventinggas pressure from the pressure housing 28 from flowing through the valve18 to the tube 146 to the lower inlet 91. The indentation 138 thatconnected the two tubes 144, 146 and the two openings 122, 120 in thestopped position of FIG. 6 is no longer aligned with these openings. Asa result the second pressure flow path 150 from the pressure housing 28to the lower inlet 91 is closed.

Additionally, in FIG. 7, the upper vent path 154 is closed. The o-ring134 a is positioned between the opening 124 and the vent port 126. Thiso-ring 134 a blocks air flow from the tube 148 to the vent port 126,thereby closing the upper vent path 154 (shown in FIG. 6). Theindentation 136 that connects the opening 124 and the vent port 126 inthe stopped position of the valve is no longer aligned with the ventport 126, so air cannot flow from the tube 146 to the vent port 126.

The valve 18 in FIG. 7 opens two additional flow paths. When the spool112 translates from the stop position in FIG. 6 to the start position inFIG. 7, the indentation 136 moves into alignment with the tube 144 andthe tube 148, thereby opening the third pressure flow path 152. Thethird pressure flow path fluidically couples the pressure housing 28 tothe upper inlet 92 of the piston assembly 26. Specifically, gas pressurefollowing the third pressure flow path 152 flows from the outlet port 38of the pressure housing 28, through the tube 144, into the opening 122of the housing 114, through the indentation 136, out of the opening 124in the housing 114, and through the tube 148 to the upper inlet 92. Thisflow path is shown by the dotted arrows in FIG. 7. Gas pressure followsthis path from the pressure housing 28 to the piston assembly 26,entering the chamber 84 through the inlet 92 and passage 92 a, above theupwardly-facing surface 105 of the piston plate 104. The gas pushes downon this surface 105 of the piston plate 104, causing the piston 30 tomove down into the deployed position (shown in FIG. 4C). The o-rings 134a, 134 b on opposite sides of the indentation 136 constrain the flow ofgas pressure from the tube 144 to the tube 148 and prevent the gas fromleaking through the valve 18 and escaping through another path.

At the same time, the valve 18 opens the lower vent path 156 to vent thechamber 84 below the piston plate 104. The lower vent path 156fluidically couples the lower inlet 91 to the vent port 128.Specifically, the lower vent path 156 passes from the lower inlet 91through tube 146, into the opening 120 in the housing 114, and throughthe indentation 138, exiting through the vent port 128. This path 156 isshown in solid arrows in FIG. 7. The o-rings 134 b and 134 c constrainthe flow of air through this flow path, providing a seal on either sideof the indentation 138 to prevent leakage of the air through the valve18.

As shown in FIGS. 6-7, the indentations 136 and 138 are sized to spanbetween the openings 120, 122, 124 and vent ports 126, 128 in order toconnect the various flow paths. Specifically, the indentation 136 issized to span between the vent port 126 and the opening 124, and betweenthe opening 124 and the opening 122. The indentation 138 is sized tospan between the opening 122 and the opening 120, and between theopening 120 and the vent port 128.

Referring to both FIGS. 6 and 7, the complete operation of the device 10is apparent. Before activation, in FIG. 6, the medication flow path 44is interrupted by the liquid seal 140 on the valve 18 to prevent flow ofmedication to the needle. The second pressure flow path 150 to the lowerinlet 91 is open, so that air pressure within that flow path lifts thepiston 30 and retains it in the retracted position, with the needle 34safely housed inside the device 10. The upper vent path 154 is open,allowing the air above the piston plate 104 to vent, so that air is nottrapped above the piston to prevent the piston from moving up into theretracted position. The third pressure flow path 152 from the pressurehousing 28 to the upper inlet 92 is closed, so that no pressure flows tothe top surface 105 of the piston plate 104 to move the pistondownwardly. The lower vent path 156 is also closed, so that the airpressure under the piston plate 104 does not vent, causing the piston 30to slide down.

In this state, the piston 30 and attached needle 34 are stored in theraised position, and the liquid medication is sealed. The device 10 canbe shipped, stored, and carried by the user until ready for use. Thedevice can be stored in various orientations, and the wide liquid seal140 prevents the liquid from flowing to the needle before the device isready for use. If the piston 30 is inadvertently pushed down duringshipment, the air inside the chamber 84 below the piston plate 104 willexert pressure back on the piston to retain it into the retractedposition. The air inside the chamber 84 under the piston plate 104 issealed (by the seal 108 at one end and the pressure housing at theother), so that the air does not leak out and allow the piston to slidedownwardly. Because there are no vent paths available to this air, theair acts as a cushion to retain the piston 30 in the raised positionduring shipment and storage.

When the user is ready to use the device 10 to inject the medication,the user first removes a cover sheet or liner 11 (see FIG. 1) from thebottom surface of the base 14 to expose an adhesive layer along thebottom surface of the base 14. The user presses this adhesive surfaceagainst the skin at the desired location of the injection. The hole 110in the base 14 indicates exactly where the needle will extend to insertinto the skin. The user can align this hole 110 with the desired pointof injection on the skin.

The user then presses the activation button 20 to generate the gaspressure inside the device. As explained above, the button 20 movesdownwardly into the pressure housing 28 and causes the two chemicalreactants 70, 72 to contact each other, thereby initiating the chemicalreaction that generates the gas pressure. At this point, the valve 18remains in the “stop” position shown in FIG. 6. As a result, while thegas pressure builds in the pressure housing 28, the medication flow path44 remains closed, and the third pressure flow path 152 remains closed.The gas pressure from the pressure housing flows through the firstpressure flow path 40 into the medication reservoir 24 and pushes themedication along the medication flow path 44 to the seal 140, where itis prevented from flowing any further. Also, pressure from the pressurehousing 28 flows through the open second pressure flow path 150 to thelower inlet 91 and into the chamber 84 below the piston plate 104. Thispressure further retains the piston in the raised, retracted position.

When the user is ready for the injection, he or she presses the startbutton 130 on the spool 112. The start and stop buttons on the spool areaccessible through windows 16 a and 16 b on the cover 12 (see FIG. 1),so the user can push the buttons to slide the spool 112 in the valve.When the user presses the start button 130, the spool 112 translateswithin the valve housing 114 to the start position shown in FIG. 7. Asdescribed above, this movement of the spool 112 opens the medicationflow path 44 (through groove 142), opens the third pressure flow path152 to the upper inlet 92, and opens the lower vent path 156. Thismovement also closes the second pressure flow path 150 and closes theupper vent path 154. As a result, gas pressure from the pressure housingnow flows through the third flow path 152 into the chamber 84, where itpresses on the top surface 105 of the plate 104. The air in the chamber84 below the piston plate 104 vents to the atmosphere through the lowervent path 156. The pressure on the top side 105 of the piston plate 104and the open vent path on the bottom side of the piston plate 104 causethe piston plate 104 to move downwardly through the chamber 84 to thedeployed position (shown in FIG. 4C). The needle 34 moves with thepiston and extends through the opening 110 into the user's skin. At thesame time, the gas pressure flowing through the first pressure flow path40 pushes on the flexible membrane 60 inside the medication reservoir,and the medication flows through the flow path 44 to the needle 34 andto the user.

Thus, when the user presses the start button, the needle automaticallyinserts and the medication automatically flows through the needle and tothe user for sub-cutaneous injection. The gas pressure flow through thethird pressure flow path 152 more quickly than the medication flowsthrough the medication flow path 44, and therefore the needle 34 isinserted before the medication reaches the needle, so that no medicationis lost.

When the medication has been fully delivered, or earlier if the userdesires, the user presses the stop button 132. The movement of the stopbutton 132 returns the spool 112 to the stop position shown in FIG. 6.This movement brings the seal 140 between the inlet 48 a and outlet 48 bon the valve housing 114, closing the medication flow path 44 andblocking any further flow of medication if not already completelydelivered. The third pressure flow path 152 and lower vent path 156 areclosed, and the second pressure flow path 150 and upper vent path 154are opened. As a result, the gas pressure above the piston plate 104 isvented, and the gas pressure is routed through the inlet 91 below thepiston plate 104, thereby raising the piston 30. Thus when the stopbutton 132 is pressed, the needle 34 automatically retracts into thedevice 10. The pressurized chamber 84 below the piston plate 104 retainsthe needle 34 within the device 10 for safe disposal. In one embodimentthe device 10 is a one-time use device that is discarded after themedication is delivered and the needle safely retracted within thedevice.

In the cycle of operation of the device 10 as just described, the devicealternates pressure and vent paths on opposite sides of the piston 30 toadvance and retract the needle. That is, in one position of the valve18, a first side of the piston 30 (the upwardly facing surface 105) isvented and the opposite side (the downwardly facing surface 107) ispressurized. When the valve is moved to the second position, thepressure and vent paths are reversed, such that the first side of thepiston is pressurized, and the opposite side is vented. The alternatingpressure and vent paths through the valve enable the piston and needleto be alternately advanced and retracted.

An embodiment of a medication delivery device 10′ is shown in FIG. 8.The device 10′ operates in the same way described above. The deviceincludes a cover 12, activation button 20, and start and stop buttons130, 132. The user presses the activation button 20 to activate achemical reaction or otherwise release the gas pressure inside apressure housing within the device. The user presses the start button130 to move a valve to the start position, to deploy the needle andallow the flow of medication to the needle. The user presses the stopbutton 132 to move the valve to the stop position to retract the needleand prevent further flow of medication. The device 10′ is packagedcompactly inside the cover 12, so that it is portable and convenient forthe user to carry. The three buttons 20, 130, 132 extending from thecover 12 are easy to operate, and the instructions for use are clear.Thus the patient can safely and easily administer the medication withoutcomplex instructions or preparations, and can safely dispose of theneedle 34 after injection. The user can administer the medication at anydesired location without the assistance of a medical professional.

In one embodiment, the device 10′ is approximately 1 inch in height,2.75 inches in length, and 2.65 inches in width.

Although the present invention has been described and illustrated inrespect to exemplary embodiments, it is to be understood that it is notto be so limited, and changes and modifications may be made thereinwhich are within the full intended scope of this invention ashereinafter claimed. For example, while screws 54 are shown for assemblyof the medication reservoir, and for attachment of the lid 86 to thepiston housing 32, other types of fasteners can be used, includingmechanical fasteners and/or adhesives, or ultrasonic welding of theplastic components, or other fastening methods. The medication reservoir24 may be integrally as one continuous piece rather than two separatecomponents attached together. Additionally, the base 14 can be used as apart of various components, such as the fill port 64 or the bottomportion of the medication reservoir or the piston assembly 26, but inalternative embodiments these features can be provided separately fromthe base 14 and can be mounted to the base.

The source of gas pressure is described above as carbon dioxidebyproduct from a reaction of citric acid and calcium carbonate, butother sources of gas pressure may be used. For example, the gas pressurecan be generated from other chemical reactants such as other acids andmetal carbonates, such as acetic acid and sodium or magnesium carbonate,or other acid solutions and alkali metal carbonates. Additional examplesof acids, carbonates, and other reactants can be found in U.S. Pat. No.5,700,245, the contents of which are incorporated herein by reference.The gas pressure can be contained within a pre-pressurized gas canisterwhich is punctured by the activation button to release the pressure.

The valve 18 above is a spool-type valve, but in other embodiments thevalve has other structures, such as a screw valve, a rotary valve orother types of valves.

The tubes 50 a, 50 b that form part of the medication flow path 44 canbe chosen according to the particular medication being dispensed, inorder to provide a flow path with the desired cross-sectional areadepending on the medication's viscosity and volume. The length and innerdiameter of the tubing can be chosen to alter the rate of flow of themedication through the tube to provide the desired rate of delivery intothe skin. The needle 34 can likewise be chosen based on the medicationand the depth, volume, and rate of injection.

Additional features may be included with the device 10 even though theyare not shown here. For example, an additional safety mechanism such asa pin may be utilized to retain the needle in the retracted positionduring shipment, prior to use. The user can remove the pin from thedevice to release the needle prior to use. Another safety mechanism suchas a latch can be activated after use to retain the used needle in theretracted position for disposal. Another option is a spring-loadedsheath that covers the needle when the needle is removed from the body.A window may be provided in the cover 12 to view the medicationreservoir 24 so that the user can see when the medication is fullyexhausted from the reservoir and the injection is complete. Otherindications that the injection is complete may be provided, such as apaddle wheel that provides an audible click when the medicationreservoir is empty. Alternatively, a tactile indicator triggered by aposition sensor could be provided for the completion of the injection.

Some features described above may be omitted in other embodiments. Forexample, when the medication is inserted into the reservoir 24 in asealed flexible bag, the flexible membrane 60 may be omitted. Gaspressure from the first pressure flow path 40 presses directly on thebag to cause the medication to flow, rather than pushing on the membrane60.

These are just a few examples of the many alternative designs andmodifications that may be provided without departing from the scope ofthe invention.

What is claimed is:
 1. A medication delivery device for injection of amedication, comprising: a medication reservoir; a pressure housing; apiston assembly comprising a piston coupled to a needle, the pistonbeing movable from a retracted position to a deployed position; and avalve fluidically coupled between the medication reservoir and theneedle and between the pressure housing and the piston assembly, whereinthe valve is movable from a first position in which the pressure housingis fluidically coupled to the piston assembly through a first fluid flowpath, to a second position in which the pressure housing is fluidicallycoupled to the piston assembly through a second fluid flow path.
 2. Themedication delivery device of claim 1, wherein the first fluid flow pathis fluidically coupled to a first side of the piston, and the secondfluid flow path is fluidically coupled to a second side of the pistonthat is opposite the first side.
 3. The medication delivery device ofclaim 2, wherein the first side of the piston comprises a downwardlyfacing surface, and the second side of the piston comprises an upwardlyfacing surface.
 4. The medication delivery device of claim 3, whereinthe piston comprises a plate having the upwardly and downwardly facingsurfaces, and wherein the plate is slidable within a piston housing tomove the piston from the retracted position to the deployed position. 5.The medication delivery device of claim 1, further comprising a thirdfluid flow path from the pressure housing to the medication reservoir.6. The medication delivery device of claim 5, further comprising amedication flow path from the medication reservoir to the needle.
 7. Themedication delivery device of claim 6, wherein the valve comprises aseal that is positioned to block the medication flow path when the valveis in the first position and a passage that is positioned to align withthe medication flow path when the valve is in the second position. 8.The medication delivery device of claim 6, further comprising a firstvent path fluidically coupling the piston assembly to a first vent portand a second vent path fluidically coupling the piston assembly to asecond vent port.
 9. The medication delivery device of claim 8, whereinthe valve comprises a first indentation that aligns with the first ventpath in the first position of the valve and aligns with the second flowpath in the second position of the valve, and wherein the valvecomprises a second indentation that aligns with the first flow path inthe first position of the valve and aligns with the second vent path inthe second position of the valve.
 10. The medication delivery device ofclaim 9, wherein the valve further comprises a second seal that ispositioned to block the first vent path in the second position of thevalve, and a third seal that is positioned to block the second flow pathin the first position of the valve and is positioned to block the firstflow path in the second position of the valve, and a fourth seal that ispositioned to block the second vent path in the first position of thevalve.
 11. A medication delivery device for injection of a medication,comprising: a medication reservoir; a pressure housing containing asource of gas pressure; a piston assembly comprising a piston coupled toa needle, the piston being movable from a retracted position to adeployed position; a first flow path from the pressure housing to thepiston assembly; and a valve fluidically coupled between the pressurehousing and the piston assembly, the valve being movable from a firstposition in which the valve blocks a flow of the gas pressure throughthe first flow path, to a second position in which the valve allows suchflow to move the piston assembly from the retracted position to thedeployed position.
 12. The medication delivery device of claim 11,further comprising a medication flow path from the medication reservoirto the needle, and wherein the valve comprises a seal that blocks themedication flow path in the first position of the valve, and wherein thevalve comprises a passage that aligns with the medication flow path inthe second position of the valve.
 13. The medication delivery device ofclaim 11, further comprising a second flow path from the pressurehousing to the piston assembly, wherein in the first position the valveallows a flow of the gas pressure through the second flow path to movethe piston assembly to the retracted position, and in the secondposition the valve blocks such flow through the second flow path. 14.The medication delivery device of claim 13, wherein the first flow pathis fluidically coupled to an upwardly facing surface of the pistonassembly, and wherein the second flow path is fluidically coupled to adownwardly facing surface of the piston assembly.
 15. The medicationdelivery device of claim 13, further comprising a third pressure flowpath from the pressure housing to the medication reservoir.
 16. Themedication delivery device of claim 11, further comprising an activationbutton attached to the pressure housing for releasing the gas pressurefrom the pressure housing.
 17. A medication delivery device forinjection of a medication, comprising: a medication reservoir; a sourceof gas pressure; and a piston assembly comprising a piston coupled to aneedle, wherein the needle is fluidically coupled to the medicationreservoir, and wherein the piston is movable, by a fluid flow from thesource of gas pressure, from a retracted position in which the needle iscontained within the medication delivery device to a deployed positionin which the needle extends from the medication delivery device, and ismovable, by the fluid flow from the source of gas pressure, from thedeployed position to the retracted position.
 18. The medication deliverydevice of claim 17, further comprising a valve fluidically coupledbetween the source of gas pressure and the piston assembly, the valvebeing movable from a first position in which the valve fluidicallyconnects the fluid flow from the source of gas pressure to a first sideof the piston to move the piston to the retracted position, to a secondposition in which the valve fluidically connects the fluid flow from thesource of gas pressure to a second opposite side of the piston to movethe piston from the retracted position to the deployed position, andback to the first position to move the piston from the deployed positionto the retracted position.
 19. The medication delivery device of claim18, wherein the valve comprises a spool valve having a plurality ofpassages and a plurality of seals for allowing and blocking the fluidflow from the source of gas pressure.
 20. A method for injectingmedication, comprising: providing a medication delivery devicecomprising: a medication reservoir containing a medication; a pressurehousing containing a source of gas pressure; and a piston assemblycomprising a piston coupled to a needle, the piston being movable from aretracted position in which the needle is contained within themedication delivery device to a deployed position in which the needleextends from the medication delivery device; deploying the needle bycommunicating a fluid flow from the source of gas pressure to the pistonassembly; delivering the medication to the needle by communicating thefluid flow from the source of gas pressure to the medication reservoir;and retracting the needle by communicating the fluid flow from thesource of gas pressure to the piston assembly.
 21. The method of claim20, wherein deploying the needle comprises communicating the fluid flowfrom the source of gas pressure to an upwardly facing surface of thepiston, and wherein retracting the needle comprises communicating thefluid flow from the source of gas pressure to an opposite, downwardlyfacing surface of the piston.